Stereoscope
a simple and once slightly dissimilar pictures of an object are fused into one image, having the actual appearance of relief. A reflecting form of the stereoscope was invented by Professor Wheatstone in 1838. Subsequently Sir David Brewster invented the refracting or lenticular stereoscope, based on the refractive properties of semidouble convex lenses; and this instrument, of which there are numerous forms came into general use. Convex lenses magnify the pictures besides producing a stereoscopic effect. Photography greatly assists the stereoscope in providing perfectly accurate right-andleft monocular views, which are taken simultaneously on a plate in a twin camera. Several modifications of the re- Cyc-Vol. IX STEREOSCOPE flecting stereoscope are distinguished by the names pseudoscope, iconoscope, telestereoscope, and polistereoscope, the last being an apparatus which serves the purposes of all the others.